By now you are most likely finishing up your base phase of training. It is important to have an effort of at least 2 hours at the high end of zone 2 heart rate while wattage and/or pace remain the same throughout. If your wattage or pace goes down before the 2 hour mark then spend more time laying down the base.
A good bridge from this phase into the build phases are tempo (AKA cruise) intervals. They are a zone 3 effort and you will find the most benefit with these in the high end of zone 3. This is an example of these types of efforts and always begin with at least 15 minutes of warm up and end with at least 10 minutes of warm down:
T15: 5×15 minute intervals at tempo with 3 minutes off between them
T20: 5×20 minute intervals at tempo with 3 minutes off between them
T25: 4×25 minute intervals at tempo with 3 minutes off between them
T45: 2×45 minute intervals at tempo with 3 minutes off between them
As with your base workouts make sure to complete the duration properly before moving to the next. Slowly and methodically building to your objectives will help prevent burn-out and injury. It’ll also make you faster!